In the evolving time division duplex (TDD) radio communication network, the very high flexibility in downlink/uplink (DL/UL) assignment of subframes would be selected to follow the traffic variations, in which spectrum resources are dynamically assigned to either transmission direction, i.e. downlink or uplink. As such, it easily exploits unpaired spectrum allocations in the same carrier.
When switching from downlink transmission to uplink transmission, both the Evolved Node B (eNB) and the user equipment (UE) need time to complete the switching. In general, the UE needs more time than the eNB to finish the switching. Especially, a low-performance UE would have a longer switch time. In addition, the propagation delays are also different for the UEs served by the eNB due to the different distances from the eNB. Hence, a guard period (GP) is introduced between the downlink subframes and the uplink subframes to accommodate the switch time and the propagation delay. During the guard period, no payload data is transmitted from/to the eNB.
Currently, the problem for the flexible duplex is that a fixed time slot needs to be pre-defined as the guard period for DL-to-UL switching in the downlink subframe. For example, two UEs are served in one cell as shown in FIG. 1. The UE1 is a high-performance terminal with a very short DL-to-UL switch time and small propagation delay, i.e., close to the eNB, whereas the UE2 is a low-performance terminal with a relative long DL-to-UL switch time and large propagation delay, i.e., far away to the eNB. To serve both UEs in the following uplink subframe, the eNB would puncture the symbols in downlink subframes to reserve a time period long enough to be larger than the maximum DL/UL switch time plus propagation delay as the guard period for the DL-to-UL switching. In this case, even if the UE1 has finished the DL-to-UL switching, it has to wait for extra time before transmitting uplink subframe to the eNB. As a result, the spectrum efficiency is impacted badly. This is especially the case when the disparity of the DL-to-UL switching time and propagation delay among the UEs is larger.